Hello, I am a student, and I am trying to perform a fatigue analysis on Ansys. This is for a knee replacement joint. Usually joint spacers are made of UHMWPE. This is my first time doing this analysis. Every time I try to run the simulation, there is an error that asks me to define the S-N curve. However, no matter how hard I research, I am not able to find a curve that compares the alternating stress vs the cycles. I don't have a background with materials so I am not really sure where I could find this curve.
You can check if the ANSYS database of materials contains the material polyethylene. If so, you can assign that material to your model. If not, then you either will have to find the necessary data from any published work in journals or else probably perform the experiment to get the data.
I suggest that you set up the FEM analysis only to compute stress and strain values (e.g. steady-stste structural analysis), then extract the calculated values to estimate fatigue life outside the program based on SN curve data, if available. The finite element method should not be intended to be used for fatigue calculations directly, this is only a tool offered by modern software for inexperienced users
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